The conventional motorcycle disk brake lock is generally composed of a body which is provided with a slot to accommodate the disk of the disk brake. The body is U-shaped in its cross section and is provided respectively in two sides of the slot thereof with a receiving hole for disposing the lock core and the lock bolt, and with an insertion slot for receiving the end of the lock bolt. The receiving hole is provided therein with a position recovering spring for providing the force capable of keeping the lock core and the lock bolt at the unlocking position. In operation, the lock core and the lock bolt are located at the unlocking position such that the lock core juts out of the body. In operation, the disk brake of a motorcycle is received in the slot of the lock body before the lock core is pressed into the lock body such that the lock bolt is inserted into the insertion slot via one of the cooling holes of the disk brake. The motorcycle disk brake is thus locked.
Such a conventional motorcycle disk brake lock as described above is defective in design in that the lock body can be easily tampered with by inserting a foreign object into the slot of the U-shaped lock body. In order to overcome the drawback of the conventional motorcycle disk brake lock, the present invention an improved lock body which has an insertion slot provided with a retaining portion. In the meantime, the lock bolt is also improved such that the engaging end of the lock bolt is provided with a retaining portion engageable with the retaining portion of the insertion slot of the lock body at such time when the lock bolt is turned an angle of 90 degrees by means of the lock core. However, such an improvement as described above is limited in design in that a key is needed to lock the lock, thereby making it inconvenient to use, especially for an absent-minded person who has a propensity to forget to carry the key with him or her.